Grades, types and stages of large bowel and rectal neuroendocrine cancers

What are large bowel and rectal neuroendocrine cancers?

Large bowel and rectal neuroendocrine cancers are also called colorectal neuroendocrine cancers. They are cancers that start in the ​neuroendocrine cells​ of the ​large bowel (colon) or ​back passage (rectum​).

Read about the difference between NETs and NECs

Grading large bowel and rectal neuroendocrine cancers

The pathologist looks at:

• how abnormal the cancer cells look – doctors call this differentiation

• how quickly or slowly they are dividing and growing – this is grading

Differentiation

This refers to how different the neuroendocrine cancer cells look. This is in comparison to healthy neuroendocrine cells:

• Well differentiated cancers look abnormal. But they still have some similarities to normal neuroendocrine cells. These are neuroendocrine tumours (NETs).

• Poorly differentiated cancers look very abnormal. They are not like normal neuroendocrine cells at all. These are neuroendocrine carcinomas (NECs).

Grade

This is about cell division and growth rate. To describe this, you might hear the terms mitotic rate or Ki67%. The higher the mitotic rate or Ki67 %, the faster the growth.

There are 3 grades of large bowel and rectal neuroendocrine tumours (NETs):

• Grade 1 cancers grow slowly. They are low grade.

• Grade 2 grow at a moderate pace (between 1 and 3). They are intermediate grade.

• Grade 3a grow rapidly. They are high grade.

All large bowel and rectal neuroendocrine carcinomas (NECs) grow rapidly and are grade 3b.

Read more about grading neuroendocrine cancer

Types of large bowel and rectal neuroendocrine cancer

There are 2 main types of neuroendocrine cancer in the large bowel and rectum:

• large bowel and rectal neuroendocrine tumours (NETs) – these are well differentiated cancers that can be either slow or fast growing

• large bowel and rectal neuroendocrine carcinoma (NECs) - these are poorly differentiated cancers that are fast growing

Doctors also group these cancers depending on whether they start in the large bowel or rectum.

Large bowel neuroendocrine cancers

These cancers start in the large bowel. This is also called the large intestine or colon. They are different to neuroendocrine cancers that start in the small bowel.

There are different types.

Large bowel NETs

Large bowel NETs can be either slow or fast growing. They often don’t cause symptoms until they are large. At diagnosis, it is quite common to have disease which has spread to ​lymph nodes​ and to other parts of the body.

Large bowel NETs can be more difficult to treat than rectal NETs and have a worse outlook (​prognosis).

Large bowel NECs

Large bowel NECs are fast growing and have often spread to other parts of the body at diagnosis. They can also be more difficult to treat.

Rectal neuroendocrine cancers

These cancers start in the back passage (rectum). This connects the large bowel to the anus. This part of the bowel stores poo (stool) until it is ready to be passed out of the body.

There are different types.

Rectal NETs

Rectal NETs are usually slow growing. They are more common than rectal NECs.

Rectal NETs often don’t cause symptoms and are diagnosed during tests for something else. Most people have a localised rectal NET that hasn’t spread. But they can sometimes spread.

Rectal NECs

Rectal NECs are fast growing and often spread to other parts of the body. So they can be more difficult to treat.

MiNEN (mixed Neuroendocrine non Neuroendocrine Neoplasm)

You can also get neuroendocrine cancers that are made up of a mix of cell types. Doctors call this MiNEN or mixed Neuroendocrine non Neuroendocrine Neoplasm.

These cancers contain neuroendocrine cells mixed with a more common type of bowel cancer cell. Most MiNEN contain neuroendocrine cancer cells and ​adenocarcinoma​ cells. These cancers are often fast growing.

The stages of large bowel and rectal neuroendocrine cancers

The stage of a large bowel or rectal neuroendocrine cancer tells you about its size and whether it has spread. Knowing the stage can help your doctor decide which treatment you need. 

You have tests and scans which give some information about the stage of the cancer. Sometimes it’s not possible to be certain about the stage until after surgery.

There are different ways to stage large bowel and rectal neuroendocrine cancer. These include the TNM system and number staging system. Doctors usually use the TNM system.

TNM stage

In the UK, doctors usually use a staging system called TNM. TNM stands for tumour, node and metastasis:

• T describes the size of the tumour

• N describes whether there are any cancer cells in the lymph nodes

• M describes whether the tumour has spread to a different part of the body

Number staging

Your doctor might tell you the number stage of your neuroendocrine cancer. Number staging systems use the TNM system to divide cancers into stages. Most types of cancer have 4 stages, numbered from 1 to 4.

On our general staging page at the link below, you can read a brief summary of what the number stages mean for most types of cancer. Your doctor can tell you more about your own number stage.

Read more about staging neuroendocrine cancers

Below we have a simplified description of TNM staging for large bowel and rectal neuroendocrine cancer.

Tumour (T)

Tumour describes the size of the cancer. It is divided into 4 main stages. This is a simplified description of the T stages:

T1 means the cancer is no bigger than 2 cm. It has only grown into the inner lining of the bowel (the mucosa), or into the next layer (the submucosa). 

T2 means the cancer has grown into the muscle layer of the bowel wall. Or the tumour is bigger than 2 cm. 

T3 means the cancer has grown through the muscle layer and into the first part of the outer lining of the bowel wall.

T4 means the cancer has grown through the outer lining of the bowel wall into the tissue layer (peritoneum) covering the organs in the tummy (abdomen). Or it has spread into a nearby organ or structure.

Node (N)

The N stage describes whether the cancer has spread to the lymph nodes.

N0 means there are no lymph nodes containing cancer cells.

N1 means there are neuroendocrine cancer cells in the nearby lymph nodes. 

Metastases (M)

The M stage describes whether the tumour has spread to a different part of the body.

M0 means the cancer has not spread to other areas of the body.

M1 means the cancer has spread to other areas of the body, such as the liver.

Treatment for large bowel and rectal neuroendocrine cancer

The grade of your cancer helps your doctor decide which treatment you need. Treatment also depends on:

• where the cancer is and whether it has spread

• your health and general fitness

Read about treatment for large bowel and rectal neuroendocrine cancer